Gonadotropin-releasing hormone receptor antagonists and methods relating thereto

ABSTRACT

GnRH receptor antagonists are disclosed which have utility in the treatment of a variety of sex-hormone related conditions in both men and women. The compounds of this invention have the structure: 
                 
 
wherein A, R 1 , R 2 , R 3a , R 3b , R 4 , R 5 , R 6 , and n are as defined herein, including stereoisomers, prodrugs and pharmaceutically acceptable salts thereof. Also disclosed are compositions containing a compound of this invention in combination with a pharmaceutically acceptable carrier, as well as methods relating to the use thereof for antagonizing gonadotropin-releasing hormone in a subject in need thereof.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/211,972 filed Aug. 2, 2002, now U.S. Pat. No. 6,750,350 which claimsthe benefit of U.S. Provisional Patent Application No. 60/310,019 filedAug. 2, 2001, which applications are incorporated herein by reference intheir entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Partial funding of the work described herein was provided by the U.S.Government under Grant No. R43-HD38625 provided by the NationalInstitute of Health. The U.S. Government may have certain rights in thisinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to gonadotropin-releasing hormone(GnRH) receptor antagonists, and to methods of treating disorders byadministration of such antagonists to a warm-blooded animal in needthereof.

2. Description of the Related Art

Gonadotropin-releasing hormone (GnRH), also known as luteinizinghormone-releasing hormone (LHRH), is a decapeptide(pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂) that plays an importantrole in human reproduction. GnRH is released from the hypothalamus andacts on the pituitary gland to stimulate the biosynthesis and release ofluteinizing hormone (LH) and follicle-stimulating hormone (FSH). LHreleased from the pituitary gland is responsible for the regulation ofgonadal steroid production in both males and females, while FSHregulates spermatogenesis in males and follicular development infemales.

Due to its biological importance, synthetic antagonists and agonists toGnRH have been the focus of considerable attention, particularly in thecontext of prostate cancer, breast cancer, endometriosis, uterineleiomyoma, and precocious puberty. For example, peptidic GnRH agonists,such as leuprorelin (pGlu-His-Trp-Ser-Tyr-D-Leu-Leu-Arg-Pro-NHEt), havebeen used to treat such conditions. Such agonists appear to function bybinding to the GnRH receptor in the pituitary gonadotropins, therebyinducing the synthesis and release of gonadotropins. Chronicadministration of GnRH agonists depletes gonadotropins and subsequentlydown-regulates the receptor, resulting in suppression of steroidalhormones after some period of time (e.g., on the order of 2-3 weeksfollowing initiation of chronic administration).

In contrast, GnRH antagonists are believed to suppress gonadotropinsfrom the onset, and thus have received the most attention over the pasttwo decades. To date, some of the primary obstacles to the clinical useof such antagonists have been their relatively low bioavailability andadverse side effects caused by histamine release. However, severalpeptidic antagonists with low histamine release properties have beenreported, although they still must be delivered via sustained deliveryroutes (such as subcutaneous injection or intranasal spray) due tolimited bioavailability.

In view of the limitations associated with peptidic GnRH antagonists, anumber of nonpeptidic compounds have been proposed. For example, Cho etal. (J. Med. Chem. 41:4190-4195, 1998) disclosesthieno[2,3-b]pyridin-4-ones for use as GnRH receptor antagonists; U.S.Pat. Nos. 5,780,437 and 5,849,764 teach substituted indoles as GnRHreceptor antagonists (as do published PCTs WO 97/21704, 98/55479,98/55470, 98/55116, 98/55119, 97/21707, 97/21703 and 97/21435);published PCT WO 96/38438 discloses tricyclic diazepines as GNRHreceptor antagonists; published PCTs WO97/14682, 97/14697 and 99/09033disclose quinoline and thienopyridine derivatives as GNRH antagonists;published PCTs WO 97/44037, 97/44041, 97/44321 and 97/44339 teachsubstituted quinolin-2-ones as GnRH receptor antagonists; and publishedPCT WO 99/33831 discloses certain phenyl-substituted fusednitrogen-containing bicyclic compounds as GnRH receptor antagonists.

While significant strides have been made in this field, there remains aneed in the art for effective small molecule GNRH receptor antagonists.There is also a need for pharmaceutical compositions containing suchGNRH receptor antagonists, as well as methods relating to the usethereof to treat, for example, sex-hormone related conditions. Thepresent invention fulfills these needs, and provides other relatedadvantages.

BRIEF SUMMARY OF THE INVENTION

In brief, this invention is generally directed to gonadotropin-releasinghormone (GnRH) receptor antagonists, as well as to methods for theirpreparation and use, and to pharmaceutical compositions containing thesame. More specifically, the GnRH receptor antagonists of this inventionare compounds having the following general structure (I):

including stereoisomers, prodrugs and pharmaceutically acceptable saltsthereof, wherein A, R₁, R₂, R_(3a), R_(3b), R₄, R₅, R₆, and n are asdefined below.

The GNRH receptor antagonists of this invention have utility over a widerange of therapeutic applications, and may be used to treat a variety ofsex-hormone related conditions in both men and women, as well as amammal in general (also referred to herein as a “subject”). For example,such conditions include endometriosis, uterine fibroids, polycysticovarian disease, hirsutism, precocious puberty, gonadalsteroid-dependent neoplasia such as cancers of the prostate, breast andovary, gonadotrophe pituitary adenomas, sleep apnea, irritable bowelsyndrome, premenstrual syndrome, benign prostatic hypertrophy,contraception and infertility (e.g., assisted reproductive therapy suchas in vitro fertilization). The compounds of this invention are alsouseful as an adjunct to treatment of growth hormone deficiency and shortstature, and for the treatment of systemic lupus erythematosis. Thecompounds are also useful in combination with androgens, estrogens,progesterones, and antiestrogens and antiprogestogens for the treatmentof endometriosis, fibroids, and in contraception, as well as incombination with an angiotensin-converting enzyme inhibitor, anangiotensin II-receptor antagonist, or a renin inhibitor for thetreatment of uterine fibroids. In addition, the compounds may be used incombination with bisphosphonates and other agents for the treatmentand/or prevention of disturbances of calcium, phosphate and bonemetabolism, and in combination with estrogens, progesterones and/orandrogens for the prevention or treatment of bone loss or hypogonadalsymptoms such as hot flashes during therapy with a GnRH antagonist.

The methods of this invention include administering an effective amountof a GNRH receptor antagonist, preferably in the form of apharmaceutical composition, to a mammal in need thereof. Thus, in stilla further embodiment, pharmaceutical compositions are disclosedcontaining one or more GnRH receptor antagonists of this invention incombination with a pharmaceutically acceptable carrier and/or diluent.

These and other aspects of the invention will be apparent upon referenceto the following detailed description. To this end, various referencesare set forth herein which describe in more detail certain backgroundinformation, procedures, compounds and/or compositions, and are eachhereby incorporated by reference in their entirety.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, the present invention is directed generally tocompounds useful as gonadotropin-releasing hormone (GnRH) receptorantagonists. The compounds of this invention have the followingstructure (I):

including stereoisomers, prodrugs and pharmaceutically acceptable saltsthereof,

-   wherein:

A is N or CR₇;

n is 2, 3 or 4;

R₁ and R₂ are the same or different and independently hydrogen, alkyl,substituted alkyl, aryl, substituted aryl, arylalkyl, substitutedarylalkyl, heterocycle, substituted heterocycle, heterocyclealkyl,substituted heterocyclealkyl, —C(R₈)(═NR₉) or —C(NR₁₀R₁₁)(═NR₉);

or R₁ and R₂ taken together with the nitrogen atom to which they areattached form a heterocycle or a substituted heterocycle;

R_(3a) and R_(3b) are the same or different and, at each occurrence,independently hydrogen, alkyl, substituted alkyl, alkoxy, alkylthio,alkylamino, aryl, substituted aryl, arylalkyl, substituted arylalkyl,heterocycle, substituted heterocycle, heterocyclealkyl, substitutedheterocyclealkyl, —COOR₁₂ or —CONR₁₀R₁₁;

or R_(3a) and R_(3b) taken together with the carbon atom to which theyare attached form a homocycle, substituted homocycle, heterocycle orsubstituted heterocycle;

or R_(3a) and the carbon to which it is attached taken together with R₁and the nitrogen to which it is attached form a heterocycle orsubstituted heterocycle;

R₄ is arylalkyl, substituted arylalkyl, heteroarylalkyl or substitutedheteroarylalkyl;

R₅ is hydrogen, alkyl, or substituted alkyl;

R₆ is aryl, substituted aryl, heteroaryl, or substituted heteroaryl;

R₇ is hydrogen, alkyl, or substituted alkyl;

R₈ is independently hydrogen, alkyl, substituted alkyl, aryl,substituted aryl, arylalkyl, substituted arylalkyl, heterocycle,substituted heterocycle, heterocyclealkyl or substitutedheterocyclealkyl;

R₉ is independently hydrogen, alkyl, substituted alkyl, aryl,substituted aryl, arylalkyl, substituted arylalkyl, heterocycle,substituted heterocycle, heterocyclealkyl or substitutedheterocyclealkyl;

R₁₀ and R₁₁ are the same or different independently hydrogen, alkyl,substituted alkyl, aryl, substituted aryl, arylalkyl, substitutedarylalkyl, heterocycle, substituted heterocycle, heterocyclealkyl orsubstituted heterocyclealkyl; and

R₁₂ is hydrogen, alkyl, or substituted alkyl.

As used herein, the above terms have the following meaning:

“Alkyl” means a straight chain or branched, noncyclic or cyclic,unsaturated or saturated aliphatic hydrocarbon containing from 1 to 10carbon atoms, while the term “lower alkyl” has the same meaning as alkylbut contains from 1 to 6 carbon atoms. The term “higher alkyl” has thesame meaning as alkyl but contains from 2 to 10 carbon atoms.Representative saturated straight chain alkyls include methyl, ethyl,n-propyl, n-butyl, n-pentyl, n-hexyl, and the like; while saturatedbranched alkyls include isopropyl, sec-butyl, isobutyl, tert-butyl,isopentyl, and the like. Representative saturated cyclic alkyls includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like; whileunsaturated cyclic alkyls include cyclopentenyl and cyclohexenyl, andthe like. Cyclic alkyls are also referred to herein as a “homocycles” or“homocyclic rings.” Unsaturated alkyls contain at least one double ortriple bond between adjacent carbon atoms (referred to as an “alkenyl”or “alkynyl”, respectively). Representative straight chain and branchedalkenyls include ethylenyl, propylenyl, 1-butenyl, 2-butenyl,isobutylenyl, 1-pentenyl, 2-pentenyl, 3-methyl-1-butenyl,2-methyl-2-butenyl, 2,3-dimethyl-2-butenyl, and the like; whilerepresentative straight chain and branched alkynyls include acetylenyl,propynyl, 1-butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl,3-methyl-1-butynyl, and the like.

“Aryl” means an aromatic carbocyclic moiety such as phenyl or naphthyl.

“Arylalkyl” means an alkyl having at least one alkyl hydrogen atomsreplaced with an aryl moiety, such as benzyl, —(CH₂)₂phenyl,—(CH₂)₃phenyl, —CH(phenyl)₂, and the like.

“Heteroaryl” means an aromatic heterocycle ring of 5- to 10 members andhaving at least one heteroatom selected from nitrogen, oxygen andsulfur, and containing at least 1 carbon atom, including both mono- andbicyclic ring systems. Representative heteroaryls are furyl,benzofuranyl, thiophenyl, benzothiophenyl, pyrrolyl, indolyl,isoindolyl, azaindolyl, pyridyl, quinolinyl, isoquinolinyl, oxazolyl,isooxazolyl, benzoxazolyl, pyrazolyl, imidazolyl, benzimidazolyl,thiazolyl, benzothiazolyl, isothiazolyl, pyridazinyl, pyrimidinyl,pyrazinyl, triazinyl, cinnolinyl, phthalazinyl, and quinazolinyl.

“Heteroarylalkyl” means an alkyl having at least one alkyl hydrogen atomreplaced with a heteroaryl moiety, such as —CH₂pyridinyl,—CH₂pyrimidinyl, and the like.

“Heterocycle” (also referred to herein as a “heterocyclic ring”) means a4- to 7-membered monocyclic, or 7- to 10-membered bicyclic, heterocyclicring which is either saturated, unsaturated, or aromatic, and whichcontains from 1 to 4 heteroatoms independently selected from nitrogen,oxygen and sulfur, and wherein the nitrogen and sulfur heteroatoms maybe optionally oxidized, and the nitrogen heteroatom may be optionallyquaternized, including bicyclic rings in which any of the aboveheterocycles are fused to a benzene ring. The heterocycle may beattached via any heteroatom or carbon atom. Heterocycles includeheteroaryls as defined above. Thus, in addition to the heteroarylslisted above, heterocycles also include morpholinyl, pyrrolidinonyl,pyrrolidinyl, piperidinyl, hydantoinyl, valerolactamyl, oxiranyl,oxetanyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydropyridinyl,tetrahydroprimidinyl, tetrahydrothiophenyl, tetrahydrothiopyranyl,tetrahydropyrimidinyl, tetrahydrothiophenyl, tetrahydrothiopyranyl, andthe like.

“Heterocyclealkyl” means an alkyl having at least one alkyl hydrogenatom replaced with a heterocycle, such as —CH₂morpholinyl, and the like.

“Homocycle” (also referred to herein as “homocyclic ring”) means asaturated or unsaturated (but not aromatic) carbocyclic ring containingfrom 3-7 carbon atoms, such as cyclopropane, cyclobutane, cyclopentane,cyclohexane, cycloheptane, cyclohexene, and the like.

The term “substituted” as used herein means any of the above groups(i.e., alkyl, aryl, arylalkyl, heteroaryl, heteroarylalkyl, homocycle,heterocycle and/or heterocyclealkyl) wherein at least one hydrogen atomis replaced with a substituent. In the case of an oxo substituent (“═O”)two hydrogen atoms are replaced. When substituted one or more of theabove groups are substituted, “substituents” within the context of thisinvention include halogen, hydroxy, oxo, cyano, nitro, amino,alkylamino, dialkylamino, alkyl, alkoxy, alkylthio, haloalkyl, aryl,arylalkyl, heteroaryl, heteroarylalkyl, heterocycle andheterocyclealkyl, as well as —NR_(a)R_(b), —NR_(a)C(═O)R_(b),—NR_(a)C(═O)NR_(a)NR_(b), —NR_(a)C(═O)OR_(b)—NR_(a)SO₂R_(b),—C(═O)R_(a), —C(═O)OR_(a), —C(═O)NR_(a)R_(b), —OC(═O)NR_(a)R_(b),—OR_(a), —SR_(a), —SOR_(a), —S(═O)₂R_(a), —OS(═O)₂R_(a) and—S(═O)₂OR_(a). In addition, the above substituents may be furthersubstituted with one or more of the above substituents, such that thesubstituent substituted alky, substituted aryl, substituted arylalkyl,substituted heterocycle or substituted heterocyclealkyl. R_(a) and R_(b)in this context may be the same or different and independently hydrogen,alkyl, haloalkyl, substituted alkyl, aryl, substituted aryl, arylalkyl,substituted arylalkyl, heterocycle, substituted heterocycle,heterocyclealkyl or substituted heterocyclealkyl.

“Halogen” means fluoro, chloro, bromo and iodo.

“Haloalkyl” means an alkyl having at least one hydrogen atom replacedwith halogen, such as trifluoromethyl and the like.

“Alkoxy” means an alkyl moiety attached through an oxygen bridge (i.e.,—O-alkyl) such as methoxy, ethoxy, and the like.

“Alkylthio” means an alkyl moiety attached through a sulfur bridge(i.e., —S-alkyl) such as methylthio, ethylthio, and the like.

“Alkylsulfonyl” means an alkyl moiety attached through a sulfonyl bridge(i.e., —SO₂-alkyl) such as methylsulfonyl, ethylsulfonyl, and the like.

“Alkylamino” and “dialkylamino” mean one or two alkyl moiety attachedthrough a nitrogen bridge (i.e., —N-alkyl) such as methylamino,ethylamino, dimethylamino, diethylamino, and the like.

With regard to the “R₁R₂N(CR_(3a)R_(3b))_(n)—” moiety of structure (I),n may be 2, 3 or 4. Accordingly, this moiety may be represented by thefollowing structure (i) when n is 2, (ii) when n is 3, and structure(iii) when n is 4:

wherein each occurrence of R_(3a) and R_(3b) above may be the same ordifferent, and are as defined above. For example, when each occurrenceof R_(3a) and R_(3b) in structures (i), (ii) and (iii) is hydrogen, the“R₁R₂N(CR_(3a)R_(3b))_(n)—” moiety has the structure R₁R₂N(CH₂)₂—,R₁R₂N(CH₂)₃— and R₁R₂N(CH₂)₄—, respectively.

The compounds of the present invention may be prepared by known organicsynthesis techniques, including the methods described in more detail inthe Examples. However in general, the compounds of structure (I) abovemay be made by the following Reaction Schemes. All substituents in thefollowing Reaction Schemes are as defined above unless indicatedotherwise.

The compounds of structure (I) may generally be referred to assubstituted 2H-pyridazin-3-one and 1H-pyridin-2-one compounds,representative compounds of which include the following:

-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-difluoro-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-dichloro-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-chloro-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-trifluoromethyl-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-methylsulfonyl-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-chloro-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-trifluoromethyl-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-methyl    sulfonyl-benzyl)-4-(2-fluoro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-difluoro-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-dichloro-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-chloro-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-trifluoromethyl-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-methylsulfonyl-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-chloro-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-trifluoromethyl-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-methylsulfonyl-benzyl)-4-(2-fluoro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethy)-6-(2,6-difluoro-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-dichloro-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-chloro-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-trifluoromethyl-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-methylsulfonyl-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-chloro-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-trifluoromethyl-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-methylsulfonyl-benzyl)-4-(2-chloro-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-difluoro-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-dichloro-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-chloro-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-trifluoromethyl-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-methylsulfonyl-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-chloro-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-trifluoromethyl-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-methylsulfonyl-benzyl)-4-(3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-difluoro-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2,6-dichloro-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-chloro-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-trifluoromethyl-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-6-methylsulfonyl-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-fluoro-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-chloro-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-trifluoromethyl-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   2-(2-Amino-2-phenyl-ethyl)-6-(2-methylsulfonyl-benzyl)-4-(2-chloro-3-methoxy-phenyl)-5-methyl-2H-pyridazin-3-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-difluoro-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-dichloro-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-chloro-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-trifluoromethyl-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-methylsulfonyl-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-chloro-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-trifluoromethyl-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-methylsulfonyl-benzyl)-3-(2-fluoro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-difluoro-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-dichloro-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-chloro-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-trifluoromethyl-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-methylsulfonyl-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-chloro-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-trifluoromethyl-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-methylsulfonyl-benzyl)-3-(2-fluoro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-difluoro-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-dichloro-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-chloro-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-trifluoromethyl-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-methylsulfonyl-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-chloro-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-trifluoromethyl-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-methylsulfonyl-benzyl)-3-(2-chloro-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-difluoro-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-dichloro-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-chloro-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-trifluoromethyl-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-methylsulfonyl-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-chloro-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-trifluoromethyl-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-methylsulfonyl-benzyl)-3-(3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-difluoro-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2,6-dichloro-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-chloro-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-trifluoromethyl-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-6-methylsulfonyl-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-fluoro-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-chloro-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;-   1-(2-Amino-2-phenyl-ethyl)-5-(2-trifluoromethyl-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one;    and-   1-(2-Amino-2-phenyl-ethyl)-5-(2-methylsulfonyl-benzyl)-3-(2-chloro-3-methoxy-phenyl)-4,6-dimethyl-1H-pyridin-2-one.

In addition, representative compounds of the present invention alsoinclude those compounds where the primary amine of the above namedcompounds is substituted with a substituted alkyl group or a cycloalkylgroup. As described in the examples, one method of alkylating amines andamides is by reductive alkylation. There are many alternative methodswell known in the chemical arts for accomplishing the reductivealkylation procedure, and there are many alternative alkylation methods.When an aldehyde, ketone, carboxylic acid, or acid chloride is treatedwith a primary or secondary amine in the presence of a reducing agentreductive alkylation may take place. Suitable reducing agents include(but are not limited to) sodium borohydride, sodiumtriacetoxyborohydride, sodium cyanoborohydride, hydrogen gas and ahydrogenation catalyst, zinc and hydrochloric acid, iron pentacarbonyland alcoholic potassium hydroxide, formic acid, pyridine borohydride.Amines and amides may also be alkylated by the reaction of formaldehydeand a Mannich base or by the nucleophilic displacement of an alkylhalide or other leaving groups. As an example, the Mitsunobu reactionallows the alkylation of amines with primary or secondary alcohols andcarboxylic acids by activation of the hydroxyl group withtriphenylphosphine to form the leaving group triphenylphoshine oxide.Other commonly used alkylation methods are described in March, AdvancedOrganic Chemistry, 4th Ed., pp 1276-1277 (1992).

The compounds of the present invention may generally be utilized as thefree acid or free base. Alternatively, the compounds of this inventionmay be used in the form of acid or base addition salts. Acid additionsalts of the free amino compounds of the present invention may beprepared by methods well known in the art, and may be formed fromorganic and inorganic acids. Suitable organic acids include maleic,fumaric, benzoic, ascorbic, succinic, methanesulfonic, acetic,trifluoroacetic, oxalic, propionic, tartaric, salicylic, citric,gluconic, lactic, mandelic, cinnamic, aspartic, stearic, palmitic,glycolic, glutamic, and benzenesulfonic acids. Suitable inorganic acidsinclude hydrochloric, hydrobromic, sulfuric, phosphoric, and nitricacids. Base addition salts included those salts that form with thecarboxylate anion and include salts formed with organic and inorganiccations such as those chosen from the alkali and alkaline earth metals(for example, lithium, sodium, potassium, magnesium, barium andcalcium), as well as the ammonium ion and substituted derivativesthereof (for example, dibenzylammonium, benzylammonium,2-hydroxyethylanmonium, and the like). Thus, the term “pharmaceuticallyacceptable salt” of structure (I) is intended to encompass any and allacceptable salt forms.

In addition, prodrugs are also included within the context of thisinvention. Prodrugs are any covalently bonded carriers that release acompound of structure (I) in vivo when such prodrug is administered to apatient. Prodrugs are generally prepared by modifying functional groupsin a way such that the modification is cleaved, either by routinemanipulation or in vivo, yielding the parent compound. Prodrugs include,for example, compounds of this invention wherein hydroxy, amine orsulfhydryl groups are bonded to any group that, when administered to apatient, cleaves to form the hydroxy, amine or sulfydryl groups. Thus,representative examples of prodrugs include (but are not limited to)acetate, formate and benzoate derivatives of alcohol and aminefunctional groups of the compounds of structure (I). Further, in thecase of a carboxylic acid (—COOH), esters may be employed, such asmethyl esters, ethyl esters, and the like.

With regard to stereoisomers, the compounds of structure (I) may havechiral centers and may occur as racemates, racemic mixtures and asindividual enantiomers or diastereomers. Compounds of structure (I) mayalso possess axial chirality, which may result in atropisomers. All suchisomeric forms are included within the present invention, includingmixtures thereof. Furthermore, some of the crystalline forms of thecompounds of structure (I) may exist as polymorphs, which are includedin the present invention. In addition, some of the compounds ofstructure (I) may also form solvates with water or other organicsolvents. Such solvates are similarly included within the scope of thisinvention.

The effectiveness of a compound as a GnRH receptor antagonist may bedetermined by various assay methods. Suitable GNRH antagonists of thisinvention are capable of inhibiting the specific binding of GnRH to itsreceptor and antagonizing activities associated with GNRH. For example,inhibition of GNRH stimulated LH release in immature rats may bemeasured according to the method of Vilchez-Martinez (Endocrinology96:1130-1134, 1975). Briefly, twenty-five day old male Spraque-Dawleyrats are administered an GNRH antagonist in saline or other suitableformulation by oral gavage, sub-cutaneous injection, or intravenousinjection. This is followed by sub-cutaneous injection of 200 ng GnRH in0.2 ml saline. Thirty minutes after the last injection, the animals aredecapitated and trunk blood collected. After centrifugation, theseparated plasma is stored at −20° C. until determination of the LH andFSH by radioimmunoassay. Other techniques for determining the activityof GnRH receptor antagonists are well known in the field, such as theuse of cultured pituitary cells for measuring GNRH activity (Vale etal., Endocrinology 91:562-572, 1972), and a technique for measuringradioligand binding to rat pituitary membranes (Perrin et al., Mol.Pharmacol. 23:44-51, 1983).

For example, effectiveness of a compound as a GnRH receptor antagonistmay be determined by one or more of the following assays.

Rat Anterior Pituitary Cell Culture Assay of GnRH Antagonists

Anterior pituitary glands are collected from 7-week-old femaleSprague-Dawley rats and the harvested glands digested with collagenasein a dispersion flask for 1.5 hr at 37° C. After collagenase digestion,the glands are further digested with neuraminidase for 9 min at 37° C.The digested tissue is then washed with 0.1% BSA/McCoy's 5A medium, andthe washed cells suspended in 3% FBS/0.1 BSA/McCoy's 5A medium andplated into 96-well tissue culture plates at a cell density of 40,000cells per well in 200 μl medium. The cells are then incubated at 37° C.for 3 days. One pituitary gland normally yields one 96-well plate ofcells, which can be used for assaying three compounds. For assay of anGnRH antagonist, the incubated cells are first washed with 0.1%BSA/McCoy's 5A medium once, followed by addition of the test sample plus1 nM GNRH in 200 μl 0.1% BSA/McCoy's 5A medium in triplicate wells. Eachsample is assayed at 5-dose levels to generate a dose-response curve fordetermination of its potency on the inhibition of GNRH stimulated LHand/or FSH release. After 4-hr incubation at 37° C., the medium isharvested and the level of LH and/or FSH secreted into the mediumdetermined by RIA.

RIA of LH and FSH

For determination of the LH levels, each sample medium is assayed induplicates and all dilutions are done with RIA buffer (0.01M sodiumphosphate buffer/0.15M NaCl/1% BSA/0.01% NaN3, pH 7.5) and the assay kitis obtained from the Nation Hormone and Pituitary Program supported byNIDDK. To a 12×75 mm polyethylene test tube is added 100 μl of samplemedium diluted 1:5 or rLH standard in RIA buffer and 100 μl of[125I]-labeled rLH (˜30,000 cpm) plus 100 μl of rabbit anti-rLH antibodydiluted 1:187,500 and 100 μl RIA buffer. The mixture is incubated atroom temperature over-night. In the next day, 100 μl of goat anti-rabbitIgG diluted 1:20 and 100 μl of normal rabbit serum diluted 1:1000 areadded and the mixture incubated for another 3 hr at room temperature.The incubated tubes are then centrifuged at 3,000 rpm for 30 min and thesupernatant removed by suction. The remaining pellet in the tubes iscounted in a gamma-counter. RIA of FSH is done in a similar fashion asthe assay for LH with substitution of the LH antibody by the FSHantibody diluted 1:30,000 and the labeled rLH by the labeled rFSH.

Radio-Iodination of GnRH Peptide

The GNRH analog is labeled by the chloramine-T method. To 10 μg ofpeptide in 20 μl of 0.5M sodium phosphate buffer, pH 7.6, is added 1 mCiof Na125I, followed by 22.5 μg chloramine-T and the mixture vortexed for20 sec. The reaction is stopped by the addition of 60 μg sodiummetabisulfite and the free iodine is removed by passing the iodinatedmixture through a C-8 Sep-Pak cartridge (Millipore Corp., Milford,Mass.). The peptide is eluted with a small volume of 80%acetonitrile/water. The recovered labeled peptide is further purified byreverse phase HPLC on a Vydac C-18 analytical column (The SeparationsGroup, Hesperia, Calif.) on a Beckman 334 gradient HPLC system using agradient of acetonitrile in 0.1% TFA. The purified radioactive peptideis stored in 0.1% BSA/20% acetonitrile/0.1% TFA at −80° C. and can beused for up to 4 weeks.

GnRH Receptor Membrane Binding Assay

Cells stably, or transiently, transfected with GnRH receptor expressionvectors are harvested, resuspended in 5% sucrose and homogenized using apolytron homogenizer (2×15 sec). Nucleii are removed by centrifugation(3000×g for 5 min.), and the supernatant centrifuged (20,000×g for 30min, 4° C.) to collect the membrane fraction. The final membranepreparation is resuspended in binding buffer (10 mM Hepes (pH 7.5), 150mM NaCl, and 0.1% BSA) and stored at −70° C. Binding reactions areperformed in a Millipore MultiScreen 96-well filtration plate assemblywith polyethylenimine coated GF/C membranes. The reaction is initiatedby adding membranes (40 ug protein in 130 ul binding buffer) to 50 ul of[¹²⁵I]-labeled GNRH peptide (˜100,000 cpm), and 20 ul of competitor atvarying concentrations. The reaction is terminated after 90 minutes byapplication of vacuum and washing (2×) with phosphate buffered saline.Bound radioactivity is measured using 96-well scintillation counting(Packard Topcount) or by removing the filters from the plate and directgamma counting. K_(i) values are calculated from competition bindingdata using non-linear least squares regression using the Prism softwarepackage (GraphPad Software).

Activity of GnRH receptor antagonists are typically calculated from theIC₅₀ as the concentration of a compound necessary to displace 50% of theradiolabeled ligand from the GnRH receptor, and is reported as a “K_(i)”value calculated by the following equation:$K_{i} = \frac{{IC}_{50}}{1 + {L/K_{D}}}$

where L=radioligand and K_(D)=affinity of radioligand for receptor(Cheng and Prusoff, Biochem. Pharmacol. 22:3099, 1973). GnRH receptorantagonists of this invention have a K_(i) of 100 μM or less. In apreferred embodiment of this invention, the GnRH receptor antagonistshave a K_(i) of less than 10 μM, and more preferably less than 1 μM, andeven more preferably less than 0.1 μM (i.e., 100 nM).

As mentioned above, the GnRH receptor antagonists of this invention haveutility over a wide range of therapeutic applications, and may be usedto treat a variety of sex-hormone related conditions in both men andwomen, as well as mammals in general. For example, such conditionsinclude endometriosis, uterine fibroids, polycystic ovarian disease,hirsutism, precocious puberty, gonadal steroid-dependent neoplasia suchas cancers of the prostate, breast and ovary, gonadotrophe pituitaryadenomas, sleep apnea, irritable bowel syndrome, premenstrual syndrome,benign prostatic hypertrophy, contraception and infertility (e.g.,assisted reproductive therapy such as in vitro fertilization).

The compounds of this invention are also useful as an adjunct totreatment of growth hormone deficiency and short stature, and for thetreatment of systemic lupus erythematosis.

In addition, the compounds are useful in combination with androgens,estrogens, progesterones, and antiestrogens and antiprogestogens for thetreatment of endometriosis, fibroids, and in contraception, as well asin combination with an angiotensin-converting enzyme inhibitor, anangiotensin II-receptor antagonist, or a renin inhibitor for thetreatment of uterine fibroids. The compounds may also be used incombination with bisphosphonates and other agents for the treatmentand/or prevention of disturbances of calcium, phosphate and bonemetabolism, and in combination with estrogens, progesterones and/orandrogens for the prevention or treatment of bone loss or hypogonadalsymptoms such as hot flashes during therapy with a GnRH antagonist.

In another embodiment of the invention, pharmaceutical compositionscontaining one or more GnRH receptor antagonists are disclosed. For thepurposes of administration, the compounds of the present invention maybe formulated as pharmaceutical compositions. Pharmaceuticalcompositions of the present invention comprise a GnRH receptorantagonist of the present invention and a pharmaceutically acceptablecarrier and/or diluent. The GnRH receptor antagonist is present in thecomposition in an amount that is effective to treat a particulardisorder—that is, in an amount sufficient to achieve GnRH receptorantagonist activity, and preferably with acceptable toxicity to thepatient. Typically, the pharmaceutical compositions of the presentinvention may include a GnRH receptor antagonist in an amount from 0.1mg to 250 mg per dosage depending upon the route of administration, andmore typically from 1 mg to 60 mg. Appropriate concentrations anddosages can be readily determined by one skilled in the art.

Pharmaceutically acceptable carrier and/or diluents are familiar tothose skilled in the art. For compositions formulated as liquidsolutions, acceptable carriers and/or diluents include saline andsterile water, and may optionally include antioxidants, buffers,bacteriostats and other common additives. The compositions can also beformulated as pills, capsules, granules, or tablets that contain, inaddition to a GNRH receptor antagonist, diluents, dispersing and surfaceactive agents, binders, and lubricants. One skilled in this art mayfurther formulate the GnRH receptor antagonist in an appropriate manner,and in accordance with accepted practices, such as those disclosed inRemington's Pharmaceutical Sciences, Gennaro, Ed., Mack Publishing Co.,Easton, Pa. 1990.

In another embodiment, the present invention provides a method fortreating sex-hormone related conditions as discussed above. Such methodsinclude administering of a compound of the present invention to awarm-blooded animal in an amount sufficient to treat the condition. Inthis context, “treat” includes prophylactic administration. Such methodsinclude systemic administration of a GnRH receptor antagonist of thisinvention, preferably in the form of a pharmaceutical composition asdiscussed above. As used herein, systemic administration includes oraland parenteral methods of administration. For oral administration,suitable pharmaceutical compositions of GnRH receptor antagonistsinclude powders, granules, pills, tablets, and capsules as well asliquids, syrups, suspensions, and emulsions. These compositions may alsoinclude flavorants, preservatives, suspending, thickening andemulsifying agents, and other pharmaceutically acceptable additives. Forparental administration, the compounds of the present invention can beprepared in aqueous injection solutions which may contain, in additionto the GnRH receptor antagonist, buffers, antioxidants, bacteriostats,and other additives commonly employed in such solutions.

The following example is provided for purposes of illustration, notlimitation. In summary, the GnRH receptor antagonists of this inventionmay be assayed by the general methods disclosed above, while thefollowing Examples disclose the synthesis of representative compounds ofthis invention.

EXAMPLE 1 SYNTHESIS OF4-(3-METHOXYPHENYL)-5-METHYL-6-(2-FLUOROBENZYL)-2-[N-(2-PYRIDYL)ETHYL-N-METHYL]ETHYL-PYRIDAZIN-3-ONE

Step 1A 3-(3-Methoxyphenyl)-4-methyl-2(5H)-furanone

A mixture of 3-methoxyphenylacetic acid (3.32 g, 20 mmol), chloroacetone(2.02 g, 22 mmol) and potassium carbonate (6.07 g, 44 mmol) inacetonitrile (30 mL) was heated at reflux for 5 hours. The resultantmixture was cooled to room temperature, diluted with ethyl acetate (60ml), filtered through a silica gel pad, and washed with ethyl acetate(2×50 mL). The filtrate was concentrated in vacuo and the residue wastreated with ether and hexanes to give a yellowish solid (3.2 g, 78%yield). ¹H NMR (CDCl₃):2.22 (s, 3H), 3.84 (s, 3H), 4.79 (s, 2H), 6.92(m, 1H), 7.05 (m, 2H), 7.36 (m, 1H).

Step 1 B2-(2-fluorophenyl)-3-hydroxy-4-methyl-5-(3-methoxyphenyl)-2,4-cyclopentadienone

A solution of 3-(3-methoxyphenyl)-4-methyl-2(5H)-furanone (2.02 g, 10mmol) and 2-fluorobenzyladehyde (1.36 g, 11 mmol) in methanol (20 mL)was treated with sodium methoxide (0.6 g, 11 mmol) at room temperature.This mixture was stirred for 15 minutes and then heated at reflux for 3hours, cooled and poured into ice-water (40 mL). The product wasextracted with ethyl acetate (2×100 mL), the extracted was washed withbrine, dried over MgSO₄, filtered and concentrated in vacuo. The residuewas treated with ether to precipitate a yellow solid (1.5 g, 50% yield).¹H NMR (CDCl₃): 2.39 (s, 3H), 3.86 (s, 3H), 6.46 (s, 1H), 6.95 (m, 1H),7.05-7.46 (m, 5H), 8.40 (m, 1H); MS: 311 (MH⁺).

Step 1 C4-(3-methoxyphenyl)-5-methyl-6-(2-fluorobenzyl)-2H-pyridazin-3-one

A solution of2-(2-fluorophenyl)-3-hydroxy-4-methyl-5-(3-methoxyphenyl)-2,4-cyclopentadienone(310 mg, 1 mmol) and hydrazine (0.2 mL) in ethanol (5 mL) was heated atreflux for 30 minutes. The resulting solution was concentrated in vacuoand the residue was dissolved in dichloromethane, dried over sodiumsulfate, filtered and concentrated in vacuo to give the desired compoundas a colorless oil. ¹H NMR (CDCl₃): 2.14 (s, 3H), 3.27 (d, J=13.8 Hz,1H), 3.43 (d, J=13.8 Hz, 1H), 6.70-7.25 (m, 8H); MS: 325 (MH⁺).

Step 1 D4-(3-methoxyphenyl)-5-methyl-6-(2-fluorobenzyl)-2-(2-hydroxyethyl)-pyridazin-3-one

A solution of2-(2-fluorophenyl)-3-hydroxy-4-methyl-5-(3-methoxyphenyl)-2,4-cyclopentadienone(620 mg, 2 mmol) and hydroxylethylhydrazine (360 mg, 45 mmol)) inethanol (5 mL) was heated at reflux for 6 hours. The resulting solutionwas concentrated in vacuo and the residue was dissolved in ethyl acetate(80 mL), washed with brine, dried over magnesium sulfate, filtered andconcentrated in vacuo to give the desired compound as colorless oil. MS:369 (MH⁺).

Step 1 E4-(3-methoxyphenyl)-5-methyl-6-(2-fluorobenzyl)-2-(2-bromoethyl)-pyridazin-3-one

A solution of4-(3-methoxyphenyl)-5-methyl-6-(2-fluorobenzyl)-2-(2-hydroxyethyl)-pyridazin-3-one(from above) and triphenylphospine (570 mg, 22 mmol) in dichloromethane(8 mL) was treated with N-bromosuccinamide (400 mg, 22 mmol) at roomtemperature for 2 hours. The crude product was used for next step. MS:431 (MH⁺).

Step 1 F4-(3-methoxyphenyl)-5-methyl-6-(2-fluorobenzyl)-2-[N-(2-pirydyl)ethyl-N-methyl]ethyl-pyridazin-3-one

A solution of4-(3-methoxyphenyl)-5-methyl-6-(2-fluorobenzyl)-2-(2-bromoethyl)-pyridazin-3-one(10% from above) was treated with N-(2-pyridyl)ethyl-N-methylamine (27.2mg, 0.2 mmol) and the mixture was stirred at room temperature overnight.The product was purified on TLC plate (2×) with 1:1 ethylacetate-hexanes to give title compound. ¹H NMR (CDCl₃): 1.95 (s, 3H),2.40 (s, 3H), 2.90 (m, 6H), 3.80 (s, 3H), 4.01 (s, 2H), 4.30 (t, J=7.1Hz, 2H), 6.76 (s, 1H), 6.79 (d, J=7.5 Hz, 1H), 6.90 (dd, J=1.2, 8.0 Hz,1H), 7.01-7.23 (m, 6H), 7.33 (t, J=8.1 Hz, 1H), 7.55 (t, J=7.5 Hz, 1H),8.51 (d, J=4.2 Hz, 1H); MS: 487 (MH⁺).

EXAMPLE 2 SYNTHESIS OF4,6-DIMETHYL-5-BENZYL-3-(3-METHOXYPHENYL)-1-[(2R)-AMINO-2-PHENETHYL]PYRIDIN-2-ONE

Step 2A 4,6-Dimethyl-5-benzyl-1H-pyridin-2-one

To a mixture of PPA (10 g) and acetoacetamide triethylamine (2.02 g, 20mmol) was added benzylacetone (5.92 g, 5.98 mL, 40 mmol). The resultingmixture was heated at 125° C. for 3 hours. The brown mixture was pouredonto crushed ice and neutralized with solid NaHCO₃. The mixture wasfiltered to give a yellow solid, which was purified by flash column(silica, 10% MeOH/DCM) to give the pyridinone (2.29 g, 53.8%) as ayellow solid. ¹H NMR (CDCl₃) δ 2.07 (s, 3H), 2.37 (s, 3H), 3.81 (s, 2H),6.38 (s, 1H), 7.00-7.40 (m, 5H); MS (CI) m/z 214.1 (MH⁺).

Step 2B 4,6-Dimethyl-3-bromo-5-benzol-1H-pyridin-2-one

To a solution of 4,6-dimethyl-5-benzyl-1H-pyridin-2-one (2.21 g, 10.4mmol) in anhydrous acetic acid (10 mL) was added bromine (3.3 g, 1.06mL, 20.7 mL). It was stirred at room temperature for one hour. Then thereaction vessel was blew N₂ to remove bromine and evaporation removedvolatiles. The residue was partitioned between CH₂Cl₂/sat. NaHCO₃/saline(100/50/50 mL). The organic layer was dried over Na₂SO₄ and evaporationgave the brominated compound as a yellow solid (3.17 g, 100%). ¹H NMR(CDCl₃) δ 2.07 (s, 3H), 2.37 (s, 3H), 3.81 (s, 2H), 7.00-7.40 (m, 5H);MS (CI) m/z 293, 295 (MH⁺).

Step 2C4,6-Dimethyl-5-benzyl-3-bromo-1-[(2R)-(tert-butoxycarbonylamino)-2-phenethyl]pyridin-2-one

A solution of N-(t-butyloxycarbonyl)-D-α-phenylglycinol (1.02 g, 4.21mmol) in anhydrous THF (15 mL) was treated with4,6-dimethyl-3-bromo-5-benzyl-1H-pyridin-2-one (1.25 g, 4.28 mmol) andtriphenylphosphine (1.6 g, 6.23 mmol) at ambient temperature, thendi-tert-butylazodicarboxylate (1.5 g, 6.5 mmol) was introduced. Thereaction mixture was stirred at ambient temperature for 16 h andvolatiles were evaporated. The residue was partitioned between sat.NaHCO₃ and EtOAc. The organic layer was dried over Na₂SO₄, evaporated,purified by flash column (silica, 20% EtOAc/Hexane) to give theprotected compound as a yellow syrup (0.21 g, 14.8%). MS (CI) m/z 511.1,514.1 (MH⁺-Boc).

Step 2D4,6-dimethyl-5-benzyl-3-(3-methoxyphenyl)-1-F[(2R)-(tert-butoxycarbonylamino)-2-phenethyl]pyridin-2-one

4,6-Dimethyl-5-benzyl-3-bromo-1-[(2R)-(tert-butoxycarbonylamino)-2-phenethyl]pyridin-2-one(0.1 g, 0.2 mmol) in benzene/EtOH/ethylene glycol ether (2/0.2/2.2 mL)was added 3-methoxyphenylboronic acid (38 mg, 0.25 mmol) and saturatedBa(OH)₂/water (˜0.5 M, 1.5 mL). The reaction mixture was deoxygenatedwith N₂ for 10 min, tetrakis(triphenylphosine) palladium (0) (46.2 mg,0.04 mmol) was added and the reaction mixture was heated at 80° C.overnight under the protection of N₂. The reaction mixture waspartitioned between brine and EtOAc. The organic layer was dried overNa₂SO₄, evaporated, purified by flash column (silica, 30% EtOAc/Hexane)to give the protected compound (0.14 g, 0.26 mmol). MS (CI) m/z 539.2(MH⁺).

Step 2E4,6-Dimethyl-5-benzyl-3-(3-methoxyphenyl)-1-[(2R)-amino)-2-phenethyl]pyridin-2-one

A solution of4,6-dimethyl-5-benzyl-3-(3-methoxyphenyl)-1-[(2R)-(tert-butoxycarbonylamino)-2-phenethyl]pyridin-2-onein DCM (1 mL) was added TFA (1 mL) and the reaction mixture was stirredat ambient temperature for 1 h. Volatiles were evaporated and theresidue was dissolved in MeOH (1 mL) and purified by PE-Sciex LCMS togive the title compound (20 mg, 20.4%). MS (CI) m/z 439.2 (MH⁺).

EXAMPLE 3 SYNTHESIS OF4,6-DIMETHYL-5-BENZYL-3-(2-FLUORO-3-METHOXYPHENYL)-1-[(2R)-AMINO-2-PHENETHYL]PYRIDIN-2-ONE

Step 3A 4,6-Dimethyl-5-benzyl-3-(2-fluoro-3-methoxyphenyl)-1-[(2R)-(tert-butoxycarbonylamino)-2-phenethyl]pyridin-2-one

4,6-Dimethyl-5-benzyl-3-bromo-1-[(2R)-(tert-butoxycarbonylamino)-2-phenethyl]pyridin-2-one(from Step 2C, 0.1 g, 0.2 mmol) in benzene/EtOH/ethylene glycol ether(2/0.2/2.2 mL) was added 2-fluoro-3-methoxyphenylboronic acid (40 mg,0.25 mmol) and saturated Ba(OH)₂/water (˜0.5 M, 1.5 mL). The reactionmixture was deoxygenated with N₂ for 10 min, tetrakis(triphenylphosine)palladium (0) (46.2 mg, 0.04 mmol) was added and the reaction mixturewas heated at 80° C. overnight under the protection of N₂. The reactionmixture was partitioned between brine and EtOAc. The organic layer wasdried over Na₂SO₄, evaporated, purified by flash column (silica, 30%EtOAc/Hexane) to give the protected compound without furtherpurification. MS (CI) m/z 557.2 (MH⁺).

Step 3B4,6-Dimethyl-5-benzyl-3-(2-fluoro-3-methoxyphenyl)-1-[(2R)-amino)-2-phenethyl]pyridin-2-one

A solution of4,6-dimethyl-5-benzyl-3-(2-fluoro-3-methoxyphenyl)-1-[(2R)-(tert-butoxycarbonylamino-2-phenethyl]pyridin-2-one in DCM (1 mL) was addedTFA (1 mL) and the reaction mixture was stirred at ambient temperaturefor 1 h. Volatiles were evaporated and the residue was dissolved in MeOH(1 mL) and purified by PE-Sciex LCMS to give the title compound. MS (CI)m/z 457.2 (MH⁺).

It will be appreciated that, although specific embodiments of theinvention have been described herein for purposes of illustration,various modifications may be made without departing from the spirit andscope of the invention. Accordingly, the invention is not limited exceptas by the appended claims.

All of the above U.S. patents, U.S. patent application publications,U.S. patent applications, foreign patents, foreign patent applicationsand non-patent publications referred to int his specification and/orlisted in the Application Data Sheet are incorporated herein byreference, in their entirety.

1. A compound having the following structure:

or a stereoisomer, or pharmaceutically acceptable salt thereof, wherein:A is N; n is 2, 3 or 4; R₁ and R₂ are the same or different andindependently hydrogen, alkyl, substituted alkyl, aryl, substitutedaryl, arylalkyl, substituted arylalkyl, heterocycle, substitutedheterocycle, heterocyclealkyl, substituted heterocyclealkyl,—C(R₈)(═NR₉) or —C(NR₁₀R₁₁)(═NR₉); or R₁ and R₂ taken together with thenitrogen atom to which they are attached form a heterocycle or asubstituted heterocycle; R_(3a) and R_(3b) are the same or differentand, at each occurrence, independently hydrogen, alkyl, substitutedalkyl, alkoxy, alkylthio, alkylamino, aryl, substituted aryl, arylalkyl,substituted arylalkyl, heterocycle, substituted heterocycle,heterocyclealkyl, substituted heterocyclealkyl, —COOR₁₂ or —CONR₁₀R₁₁;or R_(3a) and R_(3b) taken together with the carbon atom to which theyare attached form a homocycle, substituted homocycle, heterocycle orsubstituted heterocycle; or R_(3a) and the carbon to which it isattached taken together with R₁ and the nitrogen to which it is attachedform a heterocycle or substituted heterocycle; R₄ is arylalkyl,substituted arylalkyl, heteroarylalkyl or substituted heteroarylalkyl;R₅ is hydrogen, alkyl, or substituted alkyl; R₆ is aryl, substitutedaryl, heteroaryl, or substituted heteroaryl; R₇ is hydrogen, alkyl, orsubstituted alkyl; R₈ is independently hydrogen, alkyl, substitutedalkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl,heterocycle, substituted heterocycle, heterocyclealkyl or substitutedheterocyclealkyl; R₉ is independently hydrogen, alkyl, substitutedalkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl,heterocycle, substituted heterocycle, heterocyclealkyl or substitutedheterocyclealkyl; R₁₀ and R₁₁ are the same or different independentlyhydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl,substituted arylalkyl, heterocycle, substituted heterocycle,heterocyclealkyl or substituted heterocyclealkyl; and R₁₂ is hydrogen,alkyl, or substituted alkyl.
 2. The compound of claim 1 wherein R₁ ishydrogen, alkyl, substituted alkyl, arylalkyl, substituted arylalkyl,heterocyclealkyl or substituted heterocyclealkyl.
 3. The compound ofclaim 1 wherein R₄ is arylalkyl, substituted arylalkyl, orheteroarylalkyl.
 4. The compound of claim 1 wherein R₆ is aryl,substituted aryl, or heteroaryl.
 5. A pharmaceutical compositioncomprising a compound of claim 1 and a pharmaceutically acceptablecarrier or diluent.
 6. A compound according to claim 1, wherein: n is 2;R_(3a) is hydrogen at each occurrence; R_(3b) is hydrogen at oneoccurrence and aryl or substituted aryl at the other occurrence; and R₁and R₂ are independently hydrogen, alkyl or substituted alkyl.
 7. Acompound according to claim 6, wherein: R_(3b) is hydrogen at oneoccurrence and phenyl at the other occurrence; and R₁ and R₂ are eachhydrogen.
 8. A compound according to claim 6, wherein R₅ is hydrogen oralkyl.
 9. A compound according to claim 8, wherein R₅ is methyl.
 10. Acompound according to claim 8, wherein R₆ is aryl or substituted aryl.11. A compound according to claim 10, wherein R₆ is phenyl orsubstituted phenyl.
 12. A compound according to claim 11, wherein R₆ is2-fluorophenyl, 2-chlorophenyl, 2-fluoro-3-methoxyphenyl,2-chloro-3-methoxyphenyl or 3-methoxyphenyl.
 13. A compound according toclaim 10, wherein R₄ is arylalkyl or substituted arylalkyl.
 14. Acompound according to claim 13, wherein R₄ is benzyl or substitutedbenzyl.
 15. A compound according to claim 14, wherein R₄ is2-fluorobenzyl, 2-chlorobenzyl, 2-trifluoromethylbenzyl,2-methylsulfonylbenzyl, 2,6-difluorobenzyl, 2,6-dichlorobenzyl,2-fluoro-6-chlorobenzyl, 2-fluoro-6-trifluoromethylbenzyl, or2-fluoro-6-methylsulfonylbenzyl.
 16. A compound according to claim 7,wherein: R₄ is 2-fluorobenzyl, 2-chlorobenzyl, 2-trifluoromethylbenzyl,2-methylsulfonylbenzyl, 2,6-difluorobenzyl, 2,6-dichlorobenzyl,2-fluoro-6-chlorobenzyl, 2-fluoro-6-trifluoromethylbenzyl, or2-fluoro-6-methylsulfonylbenzyl; R₅ is methyl; and R₆ is 2-fluorophenyl,2-chlorophenyl, 2-fluoro-3-methoxyphenyl, 2-chloro-3-methoxyphenyl or3-methoxyphenyl.
 17. A pharmaceutical composition comprising a compoundaccording to claim 6 and a pharmaceutically acceptable carrier ordiluent.
 18. A pharmaceutical composition according to claim 17,wherein: R_(3b) is hydrogen at one occurrence and phenyl at the otheroccurrence; and R₁ and R₂ are each hydrogen.
 19. A pharmaceuticalcomposition comprising a compound according to claim 13 and apharmaceutically acceptable carrier or diluent.
 20. A pharmaceuticalcomposition according to claim 19, wherein: R₄ is 2-fluorobenzyl,2-chlorobenzyl, 2-trifluoromethylbenzyl, 2-methylsulfonylbenzyl,2,6-difluorobenzyl, 2,6-dichlorobenzyl, 2-fluoro-6-chlorobenzyl,2-fluoro-6-trifluoromethylbenzyl, or 2-fluoro-6-methylsulfonylbenzyl; R₅is methyl; and R₆ is 2-fluorophenyl, 2-chlorophenyl,2-fluoro-3-methoxyphenyl, 2-chloro-3-methoxyphenyl or 3-methoxyphenyl.